The following information obtained from UNAVCO's online DOI system:
(https://www.unavco.org/data/doi/search/search.html)

Santorini GPS Network - RIBA-Port Riba P.S.
Start: 26-Aug-2011
End: 22-Feb-2016
Newman, Andrew, 2011, Santorini GPS Network - RIBA-Port Riba P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T52Z13N7